1. Field of the Invention
The present invention relates to a fluidized bed reactor including a cyclone for fine dust separation, and a dust conveying conduit to return the dust to the fluidized bed.
During operation of a fluidized bed having changing particle sizes, and especially during fluidized bed combustion, for instance, of graphite, fine material is carried out of the fluidized bed together with the exhaust gas, and the fine material must be separated from the exhaust gas and returned into the fluidized bed or further conducted elsewhere (for example, bunkered). It is difficult to separate the fine material or dust from the exhaust gas when the fine dust possesses poor flow properties.
2. Discussion of the Prior Art
As has been known for a considerable period of time, the separation of the fine dust material from the exhaust gas and the return of the fine dust into the fluidized bed during a graphite combustion could not be achieved by means of a system located within the fluidized bed reactor and consisting of a cyclone with an attached dust return conduit extending to the lower region of the fluidized bed layer. In contrast therewith, for a long period external separator systems have been employed in which the dust is recycled into the fluidized bed either with the aid of a gate valve or an injection system positioned downstream thereof.
Disadvantages of these systems reside in the large demand for mechanically articulated components, the cooling of the dust material prior to re-entry into the fluidized bed and, above all, the flow and blockage problems encountered in the bunker and the material return system.